A hitch in producing an explosive substance may delay indefinitely the renewal of Britain's Trident nuclear missiles.

"Fogbank", as the substance is codenamed, is essential to extending the service life of W76 warheads assembled at Aldermaston in Berkshire. Last year, parliament voted to renew Trident when its design life ends in the 2020s, and build a £20bn fleet of new nuclear submarines to carry the missiles.

Problems with the substance, classified but thought to be a highly explosive and toxic solvent cleaning agent, have arisen at the Y-12 complex at Oak Ridge in Tennessee, which is extending the usable life of warheads for both the US and British versions of Trident. A spokesman for the US National Nuclear Security Administration (NNSA), which runs Y-12, confirmed that the refurbishment had run into difficulties, but would not elaborate: "The only thing we can say is there's an issue with the W76 life extension programme. It's been delayed a bit, but we have all our experts working on it."

Last year, Thomas D'Agostino, the NNSA administrator, told a congressional committee that the administration was spending "a lot of money" trying to make "Fogbank" at Y-12, but "we're not out of the woods yet". The material was extremely flammable and explosive, he said, and involved dealing with toxic materials hazardous to Y-12's workforce.

In London, the Royal Society urged all states possessing nuclear materials to agree to set up a database on which the distinct chemical signatures of such materials would be recorded, helping to trace the origin of any material which ended up on the black market. Roger Cashmore, who chaired a group which produced a report for the society on nuclear terrorism, said smugglers would be deterred if they knew that after a bomb detonated, the source of its material would be traced in weeks or even days, rather than months.